360 timing ignition woes

i have a fairly built 360 that has been a great runner for the last ten years, last winter I tore the car down for a restoration but didn’t touch the engine. Some thing has changed while the engine was on the stand. It was very difficult to time and never felt as powerful as before the restoration. The engine ran great but didn’t feel like it was all there until about a month ago, that’s when it became hard to start I adjusted the timing and got it to start ok cold but then it wouldn’t run once it warmed up It would die at idle and I would have to retard the timing to get it to restart. I have replaced the ecu, coil, cap, rotor, plugs, wires, ballast, everything ignition wise I even replaced the distributor. It has gotten progressively worse and now when I crank it it won’t fire at all. All I get out of it is a back fire through the mufflers followed by a back fire through the carb. I’m at a loss. Any one have a suggestion for my next move?

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